Measuring Earthquakes

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Vocabulary

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Focus:the point beneath Earth's surface where rock that is under stress breaks, triggering an earthquake
Epicenter:the point on the surface directly above the focus
Seismic waves:vibrations that travel through Earth's surface carrying the energy released during an earthquake
P waves (primary waves):earthquake waves that press and expand the ground like an accordion
S waves (secondary waves):earthquake waves that vibrate from side to side as well as up and down movement
Surface waves:are formed from some p and s waves when they hit the surface
Seismograph:a machine that records the ground movement caused by seismic waves as they move through the Earth
Magnitude : A measurement of Earthquake strength based on seismic waves and movement along faults
Mercalli scale: It rates earthquakes according to their intensity
Richter scale:It rates the size of seismic waves as measured by a particular type of mechanical seismograph
Moment magnitude scale:A rating scale system that estimates the total energy released by an earthquake

Outline

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• Seismic waves
  • primary waves (P waves)
  • secondary waves (S waves)
  • surface waves
• Detecting Seismic Waves
  • uses seismograph
• Measuring Earthquakes
  • The Mercalli Scale
  • The Richter Scale
  • The Moment Magnitude Scale
• Locating the Epicenter
  • finds epicenter by calculating distance between p waves and s waves

Diagram

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